The invention relates generally to vehicular trailer hitches and specifically to a coupling device for converting a ball-type trailer hitch to a pintle-type trailer hitch.
Ball and socket coupling assemblies are most widely used for coupling trailers to tow vehicles. Generally, the ball is securely mounted to the rear of the tow vehicle and the socket is mounted on the trailer tongue. However, there are certain types of equipment which do not utilize ball and socket coupling assemblies. For example, trailers for construction equipment and other types of heavy duty equipment often use lunette-type of lunette-eye trailer hitches. A lunette-type trailer hitch includes a rigid, durable, hitch, eye, or torus mounted on the trailer tongue. The lunette hitch ring is typically received over an upright projecting, generally cylindrical pintle-type hitch post secured to the rear of the tow vehicle. While the lunette-type hitch provides for a certain amount of vertical pivoting of the trailer, the trailer primarily pivots in a horizontal plane. Lunette hitching arrangements have been preferred on construction equipment trailers and other types of heavy duty trailers since they are durable, strong and they obviate the need for sockets and other hitching structure which is subject to corrosion, dirt collection and deterioration when exposed to weather and severe operating conditions. However, since most tow vehicles are provided with ball and socket hitches, it is often desirable to replace or to convert the ball-type trailer hitch to a pintle-type trailer hitch.
When a ball-type trailer hitch is replaced, removal of the ball is often difficult and is always an inconvenience. After removing the ball, it is necessary to mount a hook or pintle-type coupling element in place of the ball to receive the lunette hitch ring. The entire operation is time consuming and since tow vehicles are normally used to tow a wide variety of trailer types, such a conversion is frequently necessary. Such repeated changeover of equipment is undesirable since it presents an increased likelihood of damage to the coupling elements or a mistake in attaching the ball or pintle to the rear of the tow vehicle.
In some cases, because of the inconvenience of converting between hitching arrangements, the hitch ring of a lunette-type hitch was often merely placed around the ball member of a ball-type hitch. In such a case, the downward tongue weight of the trailer was relied upon to retain the hitch ring around the ball member without any positive retaining action. This resulted in dangerous situations in which the trailer could easily break free from the tow vehicle because nothing positively held the hitch ring on the ball member. Furthermore, the fit between the hitch ring and the ball member was often sloppy, causing damage to the hitch components.
Another problem encountered, even when specially designed posts or pins were variously secured to tow vehicles, is the difficulty in accommodating various size lunette-type hitch rings. If the pin or post was sized to fit the smallest internal diameter hitch ring, a great deal of slop or play was encountered when larger hitch rings were towed with a special hitch. Such slop or play greatly increased the wear factor and shortened the useful life of the hitch apparatus.
These problems brought about the development of a type of coupling device designed to adapt ball-type hitches for receiving a lunette hitch ring. The principal problem with these prior art adapters is their complexity, and thus their relative expense. The complexity of these devices also results in adapters having many component parts, any one of which may be lost or improperly installed, making the adapter either unusable or dangerous. Furthermore, these prior art adapters generally could not accommodate a wide variety of ball sizes, or lunette hitch ring sizes. Yet when the ability to accommodate more than one size of ball or ring was provided, changing the size of the hitch often involved an operation unobvious and difficult to the inexperienced operator.